As shown in FIG. 1, an existing current-voltage conversion module, i.e., an I-V conversion module, is composed of a current output sensor 1″ and an I-V transformation circuit 2″. The larger the open-loop gain of the inverting amplifier X, the larger the bandwidth, and the faster the response time of the I-V transformation circuit 2″.
As shown in FIG. 1, φ1 and φ2 are two-phase non-overlapping clocks. As the I-V transformation circuit 2″ is of a symmetric structure, the working process of the I-V conversion module is illustrated by an example of φ1=1 (An example of φ2=1 can be understood in a same way). When φ1=1, a switch S1 is switched on, a capacitor C1 forms a negative feedback loop with the inverting amplifier X, and an input voltage of the I-V transformation circuit 2″ is constantly a middle point voltage of the inverting amplifier X. Thus, an output current I0 of the current type sensor 1″ does not flow through a parasitic capacitor C0 of the sensor and flows through the capacitor C1.
If A0 is a low-frequency open-loop gain of the amplifier, p is a bandwidth, s is a Laplace operator, and Vop is an output voltage of a branch of the I-V transformation circuit 2. With the assumption that the open-loop gain of the inverting amplifier X is A(s)=A0p/(s+p), a transfer function of the I-V conversion module can be obtained:(Vop(s))/(Io(s))=(Aop)/s[s(Co+C1)+p(Co+C1+AoC1)]  (Formula 1)
An input step signal can be derived from the formula 1, and expression of a response of the output I-V transformation circuit is:y1(t)=[(I0t)/C1]·LG/(LG+1){1−[1/(p(LG+1)t)][1−e{circumflex over ( )}(−(LG+1)pt)]}   (Formula 2)where LG=A0β, β=C1/(C0+C1).
The inventor finds the following issue in the existing technologies: it is seen from Formula 2 that the low-frequency open-loop gain A0 and the bandwidth P of the amplifier can affect the response time of the I-V transformation circuit, which results a longer response time of the I-V transformation circuit. In order to solve this issue, it is necessary to increase the open loop gain A(s) and −3 dB bandwidth p of the inverting amplifier X. In other words, the inverting amplifier X shall have a sufficiently large gain-bandwidth product (usually 10 times the inverse of the I-V conversion time). However, according to the theory, when the gain-bandwidth product increases by 2 times, power consumption of the inverting amplifier X increases by 4 times. As a result, although the method may meet the needs for establishing an I-V conversion module, power consumption by the inverting amplifier X is too high.